Read it (thanks for posting it I looked but didnt see it or any threads addressing this)

Checked it, still having issue

To address all four points:
*Turned firewall completely off, plus allowed both boinc programs (windows fw, no other fw)
*Nothing else is using the port. Netstat doesnt lie.
*Restarted computer which resets all boinc components
*This is a new install, so only 1 GPU and brand new driver set on it.

Time to time i have the same problem. Everything goes well, computing is successful while somehow BOINC Manager the connection being lost to BOINC Client. And it can not be restored.
In mean time the BOINC Client works normally (the processes are listed in task manager / process explorer).

My solution is:
Note: i use different folder for BOINC Data.
Uninstall BOINC. The BOINC client will be stopped. Computing will be ended but not lost. Delete the BOINC folder from "Program File", Do not delete "BOINC Data" folder.
Install the latest version (the same) again. All the task will become available again from 'BOINC data' folder.

After the clear installation the connection will become available without any problems. And all the tasks will be continued.

This is the only solution which works for me.
[url]BOINC Manager cannot connect to a client[/url] is useless. All the points mentioned in this thread are correct.

I am running Win 8 (32 bit & 64 bit) on multiple machines. I have discovered that if I exit BOINC, then try to restart it, it fails to connect to the Setiathome Server. I have ensured that the BOINC Manager is "allowed" in my Firewall settings. The only remedy that works, about 90% of the time, is to "repair" the installation. There have been a couple of instances, though, where I've had to remove BOINC, revert to a much older version (e.g. 5.10.45) and then reinstall 7.0.28.